Superconductor probe coil for NMR apparatus

ABSTRACT

A NMR apparatus includes a probe coil of a superconductor coil made of magnesium 2-boride formed on a surface of a substrate, and a coil bobbin around which the superconductor coil is wound. The substrate is made of a flexible organic material that contains no hydrogen atoms.

CROSS-REFERENCE OF THE RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.11/348,352, filed Feb. 7, 2006, now U.S. Pat. No. 7,295,011, which is acontinuation of U.S. application Ser. No. 10/804,106, filed Mar. 19,2004, now U.S. Pat. No. 7,053,619, the contents of which areincorporated herein by reference and relates to U.S. application Ser.No. 11/227,291, filed Sep. 16, 2005, which is a continuation of U.S.application Ser. No. 10/804,106, filed Mar. 19, 2004, now U.S. Pat. No.7,053,619.

The Japanese patent application of 2003-120208, filed on Apr. 24, 2003,on which the present application claims the priority of ParisConvention.

DESCRIPTION OF THE INVENTION

1. Field of the Invention

The present invention relates to a probe coil for a nuclear magneticresonance apparatus.

2. Related Art

In general, as NMR (Nuclear Magnetic Resonance) apparatuses, there are aCW type wherein electromagnetic wave of radio frequency is irradiatedcontinuously to a sample, and a pulse Fourier type whereinelectromagnetic waves of pulse form are irradiated to the sample. Inrecent years, the latter pulse Fourier type apparatus is represented asNMR apparatuses. In this specification, the NMR apparatus is used tomean the pulse Fourier type NMR apparatus, unless otherwise specified.

The non-patent publication 1 discloses a fundamental structure of theNMR apparatus. According to the non-patent publication 1, the NMRapparatus comprises a superconductor magnet, a probe having a probe coildisposed therein, which coil irradiates high frequency pulse magneticfield to a sample and receives free-induction decay (FID) signals, ahigh frequency power source for supplying a high frequency current tothe probe, an amplifier for amplifying the free induction decay signals,a detector for detecting the signals, an analyzer for analyzing thesignals detected by the detector, etc. There are probes having pluralcoils so as to prepare for various kinds of nuclides or detectingmethods.

The probes have, in general, both a function for irradiating the highfrequency pulse magnetic field to the sample, and a function forreceiving the free induction decay signals emitted from the sample.

A low temperature probe is one type of the probes. According to thenon-patent publication 1, the low temperature probe has a circuit ofsuperconductor, whereby the inside of the probe is cooled by lowtemperature helium gas. As the superconductor, oxide superconductors areused.

There are two advantages of the low temperature probe, one of which isan increased Q value of the coil. The Q value is expressed by the(equation 1).Q=√{square root over ( )}(L/C·1/R)  (equation 1)In the equation 1, L means inductance of a circuit, C capacitance, and Rresistance. According to the equation 1, it is seen that the smaller theelectrical resistance, the higher the Q value becomes.

The other is to increase an S/N ratio by reducing a thermal noise of thetotal circuit, since the low temperature is realized. A nose potentialis expressed by the equation 2.Vn=√{square root over ( )}(4kTΔfR)  (equation 2)

In the equation 2, k is Boltzmann constant, Ta temperature, Δf afrequency width, and R an electric resistance. According to the equation2, it is seen that the higher the temperature, the smaller the noisevoltage Vn becomes.

In case of normal metals, the lower the temperature, the smaller theelectric resistance R becomes. Accordingly, the noise voltage Vn can bemade small in proportion of at least ½ power of the electric resistance.

Related art concerning the above-mentioned technology is disclosed in apatent publication 1, wherein in order to reduce thermal noise, abird-cage type probe coil that uses a superconductor cooled to a lowtemperature is employed to improve the S/N ratio.

In this case, as the superconductor, high temperature superconductorssuch as YBCO (YB₂Cu₃O_(7−x), yttrium series superconductors) are used tothe straight part of the bird-cage type coil.

When the low temperature probe that uses the oxide superconductors isapplied to the probe coil, the following problems will arise.

(1) Generally, oxide superconductors used in the low temperature probethe YBCO thin films; it is difficult to manufacture other shapes than aflat plate, as long as the present technology is used.

(2) The oxide superconductors containing YBCO has the strong dependencyon a magnetic orientation of a transfer current. The dependency is therelationship between orientation of the magnetic field and the transfercurrent. Thus, in the thin film conductors, it will be been understoodthat a critical current will drastically drop if a magnetic fieldperpendicular to the thin film surface is applied.

(3) Further, the oxide superconductor containing YBCO worsens itscritical current if a stress is applied thereto. Thus, it is impossibleto bend the superconductor, and it was difficult to make desired shapesfreely after the thin film is formed.

As having been described, it was difficult to make probe coils of thesuperconductor having a complicated figure. Therefore, application ofthe superconductors to the probe coils was limited to only the straightportion. Further, if other superconductors are employed, superconductorssuch as a powder-in-tube superconductor wires by a conventionalextrusion process, superconductor wires with an external stabilizer,superconductor wires in which a superconductor is formed on a metallicsubstrate of good electric conductivity have an electro-magnetic shield,which surrounds the superconductor, so that generation of a highfrequency pulsating magnetic field and detection of FID signals becomeimpossible.

As is reported in the non-patent document 2, it was found that magnesium2-boride (MgB₂) exhibited superconductivity.

Features of magnesium 2-boride are as follows.

(a) The critical temperature of magnesium 2-boride is 39K, which is thehighest among metallic superconductors.

(b) The critical magnetic field at 0K is about 18 T, which belongs to ahigher group, when compared with metallic superconductor materials.

(c) According to the research (non-patent publication 3), it has beenrevealed that a wire material manufactured by the powder-in-tube processhad good bending stress characteristics, and that the critical currentwas not worsened even when a maximum bending stress of 0.88% is appliedto the wire.

Because the bending stress characteristics of magnesium 2-boride, thewire can be formed relatively freely. The wire is suitable for the lowtemperature probe coil material as it has the high critical temperatureand high critical magnetic field. However, the wire made by thepowder-in-tube using a metal tube cannot be used as the low temperatureprobe coil as magnesium 2-boride superconductor is covered with metal.

On the other hand, a method of forming a magnesium conductor by a thinfilm process has been investigated. According to the non-patentpublication 4, it is reported that a thin film of magnesium 2-boride isdeposited on a polyimide tape by a vacuum vapor deposition. Since itsbending stress characteristics seem to be good, the conductor made bythe process may be suitable for the low temperature probe.

There are following problems in constituting the low temperature probeusing the magnesium 2-boride superconductor.

(I) Although the magnesium 2-boride superconductor made by thepowder-in-tube method using a metallic tube has good bending stresscharacteristics, and high critical temperature and high criticalmagnetic field, an electric current does not flow through thesuperconductor in the metal tube because the metallic tube surroundingthe conductor becomes the magnetic shield.

Further, it is difficult to keep the shape of the magnesium 2-boridesuperconductor as it is, when the outer metal is removed by a mechanicalor chemical process.

(II) In a method wherein the magnesium 2-boride superconductor isdeposited on the polyimide tape by the vacuum vapor deposition, thepolyimide tape which is an electric insulator is not an electromagneticshield, but since polyimide contain hydrogen atom nuclides therein whichare the most important subject to be measured in NMR, analysis wasdifficult because measurement spectrum always includes the spectrumstemming from hydrogen contained in polyimide that is superposed on themeasured spectrum.

(III) The present inventors have conducted experiments for formingmagnesium 2-boride superconductor thin film by the vacuum vapordeposition method. However, it has been revealed that the criticalcurrent of the superconductor thin film formed on polyimide tape wasonly ½ to 1/10 those of superconductors formed on a ceramic substrate ora single crystal substrate.

In order to investigate the cause, the composition of the polyimide tapewas analyzed to find that the number of hydrogen atoms was reduced.

Further, it has been revealed that the number of water moleculesincreased in the magnesium 2-boride superconductor thin film.

From the above facts, it is conceived that hydrogen atoms spin out, byvirtue of heating at the time of vacuum evaporation and they diffuseinto the magnesium 2-boride thin film formed on the surface, and theyreact with oxygen atoms that remain in the thin film to produce watermolecules.

The degradation of the critical current density of the magnesium2-boride superconductor thin film may be caused by the water molecules.Accordingly, formation of the magnesium 2-boride superconductor thinfilm by the vacuum vapor deposition method is not preferable for thenormal polyimide tape containing hydrogen atoms.

Non-patent publication 1; (A Book of NMR) (written by Youji Arata,Maruzen Publication, 2000), Part III, Measurement Technology

Patent publication 2: Japanese Patent Laid-open Hei 11-133127

Non-patent document 2: Nature 410, pages 63-64, (2001) Non-patentdocument 3: Tanaka, et al, The 66th 2002 Meeting on Cryogenics andSuperconductivity, page 148

Non-patent document 4:P. Kus et al., Applied Physics Letters, vol. 81,page 2199 (2002)

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagrammatic perspective view of a probe coil for an NMRapparatus.

FIG. 2 is a diagrammatic perspective view of a solenoide type probe coilfor an NMR apparatus.

FIG. 3 is A block diagram of an NMR probe and a measurement system forNMR signals.

FIG. 4 is a perspective view of a magnesium 2-boride formed on anorganic polymer substrate by a vacuum vapor deposition method.

FIG. 5 is a diagrammatic view of an example of a process formanufacturing a birdcage type probe coil.

FIG. 6 is a diagrammatic view of an example of a process formanufacturing a solenoide type probe coil which has a conductor wound ona bobbin.

FIG. 7 is a diagrammatic view of an example of a process formanufacturing a solenoide type probe coil which has laminatedconductors.

FIG. 8 is a diagrammatic view of an example of a process formanufacturing a saddle type probe coil.

FIG. 9 is a diagrammatic view of a magnesium 2-boride superconductor,which is covered with an insulator of an organic polymer material, thesuperconductor being formed on an organic polymer substrate by a vacuumvapor deposition method.

FIG. 10 is a diagrammatic view of a superconductor manufactured by apowder-in-tube method wherein magnesium 2-boride powder is used as thesuperconductor, and an organic polymer is used as an insulator.

FIG. 11 is a diagrammatic view of an example of an NMR apparatus thathas a superconductor probe for the NMR apparatus according to thepresent invention.

FIG. 12 is a diagrammatic view of another example of an NMR apparatusthat has a superconductor probe for the NMR apparatus according to thepresent invention.

SUMMARY OF THE INVENTION

The present inventors noticed that the useful characteristics of themagnesium 2-boride superconductor, and conducted investigation whethermagnesium 2-boride can be used as a low temperature probe coil for NMRof a solenoide type or not. As a result, the following means was appliedin order to solve the problems.

As a first means, a superconductor using the magnesium 2-boride isformed on the surface of a flexible organic polymer material as the NMRapparatus probe coil.

As mentioned before, the magnesium 2-boride has good bending stresscharacteristics; thus it is possible to bend the substrate freely and iscapable of forming desired shapes of probe coils, when thesuperconductor film is formed on the flexible organic polymer substrate.

A second means is that as the above-mentioned substrate, an organicpolymer material that contains no hydrogen atoms is used.

In many cases, spectrum of hydrogen atoms are measured by the NMRapparatus; when a substrate that does not contain hydrogen atoms isused, spectrum of hydrogen atoms does not superpose on the measuredspectrum so that accurate measurement of the sample by the NMR apparatusbecomes possible.

A third means is to substitute all or part of hydrogen atoms with heavyhydrogen atoms.

Since nuclear resonance frequencies of heavy hydrogen and hydrogen aredifferent, there is no influence of the substrate on the measured samplespectrum. Further, although the use of a substrate where all of thehydrogen atoms are substituted with heavy hydrogen is ideal, a substrateof which part of hydrogen atoms are substituted with heavy hydrogenatoms.

That is, there is no big influence on measurement if the strength of anNMR signal from hydrogen atoms contained in the substrate is weaker thanthat of an NMR signal from hydrogen atoms contained in the sample.

A fourth means is that the above-mentioned probe coil is constituted byany one of the saddle type, the bird cage type, the Helmholtz type, theone-turn type, the solenoide type, the pancake type and the combinationsthereof.

When the above-mentioned probe coil is manufactured from the oxidesuperconductor, it is difficult to make coils for NMR apparatuses havingdesired shapes because of anisotropy with respect to the magnetic fieldof the superconductor. Further, in case of metal superconductors such asa superconductor made of a single element of NB, alloy superconductor ofNbTi, cooling by liquid helium is necessary because of their lowcritical temperatures. In addition to the above, in case of compoundmetal series superconductors, their stress characteristics are bad, andmaking the desired shape of the probe coils is difficult, in general.

However, in case of manufacturing with magnesium 2-boride, there is nomagnetic anisotropy, the critical temperature is relatively high, andstress characteristics are good. Accordingly, it is possible to realizethe probe coils for NMR apparatuses with a high Q value, and a high S/Nratio, by employing the above-mentioned first, second and third means.

EMBODIMENTS OF THE INVENTION Example 1

FIG. 1 is a diagrammatic perspective view showing a saddle type probecoil for the NMR apparatus according to the present invention.

A coil 1 is constituted by two saddle type coils which are disposed atan outer periphery of a glass sample tube 3 so as to face each other.The glass sample tube 3 contains a sample to be measured.

The material of the coil 1 is magnesium 2-boride superconductor wire.The coil 1 constituted by one turn of two saddle type, and desired shapeor the number of turns can be employed if the shape and the number ofturns are the same.

The current leads 5 a, 5 b are bonded by soldering to the both ends ofthe coil 1. When current flows between the current leads 5 a, 5 b, therespective saddle coils generate magnetic fields in the direction ofarrow 6; a homogeneous magnetic field can be applied in the direction 6of the arrow at the center of the sample 4. The components are placed inthe high homogeneous static magnetic field generated by thesuperconductor magnet. The direction of the high homogeneous staticmagnetic field is in the direction 2.

Although the coil 1 may be wound on a bobbin, a material of the coilbobbin should be a material having a specific magnetic ratio nearly 1,that is, the material should be one that has a magnetic transmissionratio which is almost the same as that of vacuum.

Since the coil 1 is supplied with a high frequency pulse current and thehigh frequency pulse magnetic field is applied, the material of thebobbin should be an insulator that does transmit the high frequencymagnetic field. Further, when the bobbin contains nuclides to bemeasured, the coil bobbin itself emits NMR signals, so that the signalscannot be distinguished from the NMR signals emitted from the measuredsample 4. Thus, the care should be taken for the selection of thematerial for the bobbin. Accordingly, the coil bobbin is preferably madeof glass containing a component for adjusting the magnetic transmission.

Not only the coil bobbin, but the sample tube 3 or a vacuum insulationwhich is formed at the outer periphery of the sample tube 3, which isnot shown in the drawing, is preferably made of the special glass.

The shape of the probe coil is not limited to the saddle type. FIG. 2shows a perspective diagrammatic view of the probe coil, which employs asolenoide type coil. In this case, the direction of magnetic fieldgenerated by the probe coil is the same direction as that of an allow 6at the center of the measurement sample 4. Thus, the direction of thehigh, homogeneous static magnetic field is perpendicular to thedirection 6 or the direction 2.

FIG. 3 shows the probe for the NMR apparatus and a measurement systemfor the NMR signal.

The probe 107 is provided with the coil 1, a condenser 108, etc. Thecoil 1 is cooled down to about 20K or lower. As preferable coolingmethods, there are a method of dipping coil 1 in liquid helium (aliquid-cooling method), a method of supplying gaseous helium fromoutside (a gas-cooling method), a method of circulating gaseous, liquidor supercritical helium by an outside compressor (a forced-flow coolingmethod), a method of cooling by heat conduction using a small GM(Gifford-McMahon) cryocooler (a cryocooler-cooling method), etc.

Although not shown in FIG. 3, the probe 107 is disposed in a homogeneousmagnetic field generated by the superconductor magnet. A high frequencypower source generates on the coil 1, and a high frequency pulse currentthat is amplified by the power amplifier 102 is applied by means of thecurrent leads 5 a, 5 b.

The frequency is calculated based on a magnetic circuit ratio of staticmagnetic field and nuclides to be measured. For example, when protonsare detected in the static magnetic field of 2.35 T, the frequency is100 MHz.

The pulse width is about several μs to several tens μs, though it maydepend on the strength of magnetic field generated by the coil 1.

The power of the high frequency pulse current is generally several tensW to several hundreds W. The high pulse power current with a desiredfrequency, a pulse width and a sequence is generated by the controller100.

In the following, operation of the NMR apparatus of the invention isexplained. When the high frequency pulse current flows in the coil 1, ahigh pulse magnetic field is applied to the measuring sample 4 in thesample tube 3.

When nuclides that emit nuclear resonance are contained in the measuringsample 4, they cause nuclear resonance. After the high frequency pulsecurrent is cut off, free induction decay (FID) signals are generated.The free induction decay signals are received by the coil 1, and thereceived signals are amplified by a pre-amplifier 103 and a signalamplifier 104.

The pre-amplifier 103 is cooled down to about 80 K so as to reducenoise. Although the cooling method of the coil is preferably employed asthe cooling method of the amplifier, the cooling medium can be nitrogeninstead of helium when the cooling medium is used. If the pre-amplifier103 can be placed in such an environment that noise is sufficientlysmall, cooling of the pre-amplifier 103 is not necessary.

The free induction decay signals that are amplified by the two stageamplifiers (103, 104) are detected by a detector 105 as signals having arange of several kHz. Further, the signals are subjected to Fourierdevelopment at a signal analyzer 106 to produce the NMR spectrum.Although there are accessories, etc. other than those described above,they are not shown.

FIG. 4 shows a perspective view of an example of a magnesium 2-boridesuperconductor formed on the organic polymer substrate, which isobtained by the vacuum vapor deposition method used in the presentinvention. As the organic polymer substrate 11, polytetrafluoroethylenesheet was used. Its thickness was about 1 mm or less; the magnesium2-boride superconductor thin film 13 is formed on the sheet.

Theoretically, since polytetrafluoroethylene is an organic polymermaterial consisting essentially of carbon and fluorine, the substratedoes not emit the NMR signals in case of the ordinary NMR apparatus.Thus, an accurate measurement of the sample is possible. The thin film13 of magnesium 2-boride superconductor formed by the vacuum vapordeposition method has a thickness of about 100 μm. When the conductorthus obtained is bent at a radius of 1 cm in the surface direction, thecritical current of the conductor was 90% or more of the current of theconductor which is not bent. It has been confirmed that the degradationof the critical current due to bending stress was very small. The thinfilm can be made by other processes.

The substrate can be organic polymer materials having flexibility suchas polyimide, polyethylene, epoxy resin, etc. It is preferable tosubstitute hydrogen atoms contained with heavy hydrogen atoms, wherebyaccurate spectrum can be obtained.

FIGS. 5 to 8 show examples of manufacturing various shapes of coils. Thesuperconductors 201, which are cut into desired shapes and stereostructures 202 of the probe coils are shown.

FIG. 5 is a bird cage type, FIG. 6 a solenoide type wherein theconductors are wound around the bobbin, FIG. 7 a solenoide type whereinring shaped conductors are laminated, and FIG. 8 an example of a methodof manufacturing a saddle type.

In manufacturing the bird age type or the saddle type coil, the sheet iscut into a desired shape, and it is wound around a bobbin. Part of thesuperconductor is removed to form capacitor therein.

On the other hand, in manufacturing a solenoide type where the conductoris wound around the bobbin, the sheet is cut into narrow stripes, andthey are wound around the bobbin. The solenoide coil wherein the ringshaped conductors are laminated uses several conductors of a donut shapecut out from the sheet, thereafter they are laminated on the co-axis,followed by electrical connection therebetween.

FIG. 9 is a diagrammatic perspective view of the superconductor whereinan organic polymer insulator is applied on the periphery of magnesium2-boride superconductor 13 formed on the organic polymer materialsubstrate 11 by the vacuum vapor deposition method.

The superconductor is prepared by bonding another polyethylene sheet onthe conductors of a stripe form cut from the conductor sheet. Organicpolymer materials other than polytetrafluoroethylene can be used.Materials of which hydrogen atoms are substituted with heavy hydrogenare preferable. Since the magnesium 2-boride superconductor does notexposed to the atmosphere when the above-mentioned structure isemployed, it is possible to prevent degradation by water, etc.

FIG. 10 is a diagrammatic perspective view of the superconductormanufactured by a powder-in-tube method using magnesium 2-boride powderas a superconductor and an organic polymer as an insulator.

The conductor shown in FIG. 10 is prepared by the powder-in-tube method.In the conventional powder-in-tube method, powder of magnesium 2-borideis packed in a metal tube, followed by extrusion treatment, etc. Forexample, a polyethylene tube is inserted into a metal tube. Powder ofmagnesium 2-boride is packed in the inside of the tube, and theextrusion treatment, etc. is carried out. Then, the metal tube isremoved to obtain a superconductor 13 of magnesium 2-boride covered withpolyethylene.

Organic polymer materials other than polytetrafluoroethylene can beused. Materials of which hydrogen atoms are substituted with heavyhydrogen atoms are preferable.

According to these methods, the conductors having no electromagneticeffect by the metal at the outer periphery using the powder-in-tubemethod can be obtained. The outer metal can be removed by chemicaldissolution with acid.

The present inventors conducted manufacture of the above-mentioned probefor the NMR apparatuses. The diameter of the saddle type coil 1 was 2cm, and the length of the straight portion was 5 cm. The number of turnof the saddle coils was 1.

The coil 1 was cooled down to about 10 K by means of the gas coolingmethod using helium gas, and the re-amplifier 103 was cooled down toabout 77K by means of the liquid-cooling method using liquid nitrogen.The thus prepared probe for the NMR apparatus was placed in a highhomogeneous static magnetic field of 2.35 T; spectrum of proton NMR inethanol was measured using a high frequency power source of 100 MHz,which is a resonance frequency of proton.

Further, a probe was prepared for comparison wherein the coil 1 was madeof copper. The proton NMR spectrum was measured, while coil 1 and thepre-amplifier 103 were kept at room temperature without cooling.

As a result of a series of tests, as for the S/N ratio, the probe usingthe magnesium 2-boride superconductor wire as the coil 1 was 5 timesbetter than the probe using copper. And Q value of the former was 10times better than the latter.

As having been described above, it was possible to realize the probecoil for NMR apparatus with improved Q value and S/N ratio by using asthe probe coil the superconductor constituted by magnesium 2-boridesuperconductor.

An example of an NMR apparatus equipped with the superconductor probefor the NMR apparatus according to the present invention is shown inFIG. 11.

The coil 1 disposed in the probe 107 is a coil that uses magnesium2-boride. The shape of the coil 1 is preferably a birdcage type whichcan generate high frequency pulse in the horizontal direction or in thedirection of direction 6. A saddle type shown in FIG. 8 is alsopreferable. A solenoide type having the center axis in the direction ofdirection 6 may be used.

Preferable superconductors for coils 1 are shown in FIGS. 4, 9 or 10.The coils 1 are cooled with vaporized gas of liquid helium for coolingthe probe, the liquid being stored in a cryostat 401. In this apparatusthe gas-cooled method is employed, the coil 1 may be cooled by theabove-mentioned methods such as the liquid-cooling method, theforced-cooling method, or the cryocooler-cooling method.

If the temperature of the coil 1 is 39 K, which is the criticaltemperature of magnesium 2-boride or lower is acceptable, but about 10Kor lower is preferable to attain a large transport current. The coil 1to which the controller 100, the high frequency power source 101 and thepower amplifier 102 are connected can generate the high frequency pulsemagnetic field.

The coil 1 receives FID signals from the sample 4 placed in the sampletube 3, and the signals are amplified by the pre-amplifier 103 and thesignal amplifier 104, then the signals are detected by the detector 10so that the NMR spectrum is obtained by means of the signal analyzer106. The pre-amplifier 103 is placed in the cryostat 501 and is cooledby liquid nitrogen for the pre-amplifier to 77K so as to lessen noise.

The probe 107 is placed in a room temperature bore, which passesthrough, in the vertical direction, the cryostat 303 that accommodatesthe superconductor coil 301 and liquid helium 302. The superconductor301 is the solenoide type coil, which can generate the static magneticfield in the vertical direction 2. The superconductor coil 301 can beconstituted by plural coils so that high homogeneous static magneticfield is formed at the position of the sample 5.

In order to compensate an abnormal magnetic field due to outerturbulence or anisotropy of the superconductor coils 301, it ispreferable to install a superconductor or normal conductor coil thatgenerates magnetic field in the direction other than the direction 2.According to the above mentioned measures, an NMR apparatus having ahigh Q value and the high S/N ratio will be realized.

Further, FIG. 12 shows a concrete example of an NMR apparatus which isprovided with the superconductor probe for the NMR apparatus.

The point of FIG. 12 different from that of FIG. 11 is that thedirection 2 of static magnetic field, which is generated by thesuperconductor coil 301 is the horizontal direction, while in FIG. 11,the direction is on the vertical direction. Another point is that thedirection 6 of the high frequency pulse magnetic field generated by thecoil 1 is horizontal in case of FIG. 11, while the direction in case ofFIG. 12 is vertical.

In order to place the probe 107 at room temperature, a preferablesuperconductor coil 301 is a symmetric type coil, which is called asplit type. Plural coils are acceptable, as same as in the case of FIG.11. Installment of a shim coil is preferable. When the superconductor301 is the split coil type, the height of the apparatus can be madelower than the case shown in FIG. 11.

According to the present invention, desired shapes can be made; there isno degradation of characteristics caused by hydrogen duringmanufacturing the superconductors; hydrogen spectrum is not superposed,while measuring the NMR signals; the probe for the NMR apparatus havingno electro-magnetic shield effect by metal sheath of the conductor canbe provided.

1. A NMR apparatus comprising a superconductor magnet, a probe coil of asuperconductor coil made of magnesium 2-boride formed on a surface of asubstrate, and a coil bobbin around which the superconductor coil iswound, wherein the substrate is made of a flexible organic material thatcontains no hydrogen atoms.
 2. The NMR apparatus according to claim 1,wherein the probe coil is constituted by any one of a saddle type, abird cage type, a Helmholz type, a one-turn type, a pancake type andcombinations thereof.
 3. The NMR apparatus according to claim 1, whereinthe coil bobbin is made of glass.
 4. The NMR apparatus according toclaim 1, wherein a material of the coil bobbin has a specific magneticratio of nearly
 1. 5. The NMR apparatus according to claim 1, wherein amagnetic transmission of the coil bobbin is almost the same as that ofvacuum.